#include<stdio.h>
#include<math.h>
int main()
{
	double  n = 0.0;
	int i = 0;
	double sinx = 0.0;
	double x = 0.0;
	double y = 1.0;
	int sign = -1;
	scanf("%lf", &n);
	for (i = 1; ; i+=2)
	{
		sign = sign * -1;//开关，用于改变正负号，奇数项为正，偶数项为负
		x = pow(n, i);//计算n的奇数次方
		sinx = sinx + sign * x / y;//先把i=1的y带入，再计算3的阶乘，再计算5的阶乘
		y = y * (i + 1) * (i + 2);//计算奇数的阶乘
		if (fabs(x/y) < 0.00005)
		{
			break;
		}
	}
	printf("%.3lf\n", sinx);
	return 0;
} 